The sockaddr_l2 address type is used with AF_BLUETOOTH sockets using the
BTPROTO_L2CAP protocol.

Change-Id: I263cfd3bb5920a8c1187ead6c2e0527276575d9f
Reviewed-on: https://go-review.googlesource.com/89475Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>